Abstract Asian American women experience more favorable cancer survival than other US racial/ethnic groups, even after accounting for known prognostic indicators. Breast cancer, which follows this pattern, is a useful model for understanding factors contributing to this intriguing survival advantage, given that it is the most common cancer in Asian American women, and has established clinical, biological/genetic, and lifestyle prognostic factors. Thus, studying the breast cancer survival advantage in Asian American women has the potential to identify protective factors that may benefit all patients. We propose to investigate multilevel factors (health behaviors and contextual factors, clinical characteristics, treatment, and tumor immune response) in relation to overall and breast cancer-specific mortality in Asian American breast cancer cases. However, the Asian American population is heterogeneous, with lifestyle factors and disease risks (e.g., breast cancer survival rates) varying by specific ethnicity and by immigration status. Many studies have shown the importance of population disaggregation to uncovering meaningful differences among Asian American ethnic groups, but no single study to date includes adequate Asian American ethnic group population samples. To overcome this limitation, we will conduct the proposed research in integrated data and biospecimens from four established cohort studies enriched with Asian American breast cancer cases. These studies together include 4,219 Asian American patients (1,848 Chinese, 602 Japanese, 1,538 Filipinas) and 5,386 non-Latina White women with breast cancer as a comparison group. In Specific Aim 1, we will assess contributions of individual-level lifestyle and health behaviors and multilevel neighborhood social context and sociocultural factors to survival differences among the Asian American ethnic groups relative to non-Latina Whites. In Specific Aim 2, we will evaluate how specific treatment factors impact survival for 4,373 Asian Americans compared to 4,373 non- Latina Whites, taking advantage of electronic health record data from an equal-access healthcare system. In Specific Aim 3, we will characterize the immune infiltrates in the breast tumor microenvironment from 1,200 Asian American (from Aim 1) and 714 non-Latina White (from TCGA) patients using immunogenomic profiling, and to determine the associations of immune phenotypes with patient survival among Asian Americans and with exposure factors from Aim 1. Thus, using existing resources, this study will comprehensively assess factors including health behaviors and neighborhood context, lifestyle, treatment, tumor immuno-biology, and their contributions to the survival advantage in Asian American women. The proposed study makes efficient use of data from numerous breast cancer studies to gain insight for strategies that may advance knowledge about the management of breast cancer for all women.